Main Arguments in Favor of SRM Outdoor Research and Deployment
Urgency. Current climate mitigation efforts may not cool the planet sufficiently to avoid climate catastrophe. SRM could supplement mitigation to buy extra time. This is particularly important for climate-vulnerable communities, many of which, despite having contributed little to global emissions, will feel the most severe impacts of unmitigated climate change.
Effectiveness and Timeframe. Compared to other climate mitigation measures, both SAI and MCB could cool Earth relatively quickly in regions where it is deployed (SAI on a larger scale, MCB on a smaller scale).42 Some estimates suggest that the infrastructure necessary to deploy SAI would require two decades to develop.43 Other researchers suggest it could be deployed sooner, using existing aircraft at low altitudes.44
Cost. SAI cost estimates range from $500 million per decade to $2.5 billion per year.45 MCB is estimated to cost $10 billion per year, though actual costs would depend greatly on deployment methodology.46 These figures are miniscule compared to the cost of unmitigated climate change, which the World Economic Forum estimates at $3.1 trillion per year by 2050.47
Flexibility. SRM could be deployed relatively quickly and strategically. Project Drawdown (which recommends against SRM) estimates that, if the desired effects of SRM were not achieved, the climate would return to previous conditions within months to a few years after deployment ceased.48